1. Field of the Invention
The present invention is generally related to magnetic sensors and, more particularly, to a sensor which comprises a molded insert that is shaped to be received within a metallic housing and which comprises a plurality of components that are specifically designed to facilitate assembly of the individual component parts of the sensor.
2. Description of the Prior Art
Magnetic sensors which incorporate Hall effect elements are well known to those skilled in the art. Sensors of this type are commonly used to detect the movement of magnetically permeable objects within a predefined detection zone proximate the sensor. For example, sensors of this general type are used to detect the passage of gearteeth or other magnetic protrusions extending from a rotatable object for the purpose of synchronizing the operation of various elements of an internal combustion engine. When applied in this manner, a magnetic geartooth sensor can be used to detect the rotational position of a cam shaft or other rotatable components of an internal combustion engine in order to provide the necessary signals to control the timing of the engine.
Geartooth sensors are made in several known ways. One type of geartooth sensor attaches a flexible circuit, with a Hall element attached to it, to a plastic insert which is disposed within a plastic tube. The flexible circuit is connected in electrical communication with several components, including the Hall effect element. After the insert is disposed within the plastic housing, a quantity of curable material is injected into the housing around the insert and other components and is then cured to rigidly and permanently contain the insert and related components within the housing. One disadvantage of this type of sensor is that the curing of the injected material requires a considerable time and also requires the use of a curing oven. These additional operations often require cleaning and are time consuming and costly. In addition, the frequent cleaning often requires solvents which may be harmful to the environment.
Whenever a geartooth sensor is manufactured through the use of the processes described above, the outer shape of the finished product typically must conform to a predetermined configuration that is dictated by the end use of the product. Each application of a geartooth sensor with an internal combustion engine can require a particular shape and size of the geartooth sensor so that it can be properly attached to an external object, such as the engine block or related apparatus. Regardless of the particular means used to encapsulate the geartooth sensor and determine its ultimate outer shape, the internal components of the geartooth sensor must be protected during the preliminary assembly operation prior to being potted within a plastic housing or injection molded within an outer protective housing. It would therefore be beneficial to provide a geartooth sensor which comprises an intermediate assembly configuration that is sufficiently robust to withstand both a harsh environment and rigorous handling during subsequent manufacturing processes.
U.S. Pat. No. 5,121,289, which issued to Gagliardi on Jun. 9, 1992, describes an encapsulatable sensor assembly that includes an external housing with several internal support components that are used to retain an active sensor element and an associated electrical circuit in a predetermined relationship with each other while providing a plurality of internal sequential interconnected cavities for facilitating a flow of an encapsulating material from an injection port to a vented overflow port. This assures a complete fill of the internal cavities in order to restrain the internal components within the housing. The sensor assembly provides a structure for a void free encapsulation.
U.S. Pat. No. 5,140,262, which issued to Stolfus on Aug. 18, 1992, discloses a geartooth sensor that is shaped to have its centerline placed in non intersecting relation with a center of rotation of a rotatable member. Although the Stolfus patent does not particularly show a means for encapsulation, it illustrates a geartooth sensor with a housing in which the active components of the sensor are disposed. Both the Gagliardi and Stolfus patents illustrate geartooth sensors of the general type which typically inject an encapsulant into the housing to rigidly maintain the location of the various components of the geartooth sensor. The encapsulant must then be cured in some way.